content: /*
   * Copyright 2016-present David Karnok
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package hu.akarnokd.rxjava3.operators;
  
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.atomic.*;
  
  import org.reactivestreams.*;
  
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.internal.disposables.SequentialDisposable;
  import io.reactivex.rxjava3.internal.subscriptions.SubscriptionHelper;
  import io.reactivex.rxjava3.internal.util.BackpressureHelper;
  
  /**
   * Periodically try to emit an ever increasing long value (starting from 0L)
   * or hold onto them without physical buffering until the downstream catches up.
   * @since 0.15.0
   */
  final class FlowableIntervalBackpressure extends Flowable<Long> {
  
      final long initialDelay;
  
      final long period;
  
      final TimeUnit unit;
  
      final Scheduler scheduler;
  
      FlowableIntervalBackpressure(long initialDelay, long period, TimeUnit unit, Scheduler scheduler) {
          this.initialDelay = initialDelay;
          this.period = period;
          this.unit = unit;
          this.scheduler = scheduler;
      }
  
      @Override
      protected void subscribeActual(Subscriber<? super Long> s) {
          IntervalBackpressureSubscription ibs = new IntervalBackpressureSubscription(s);
          s.onSubscribe(ibs);
          ibs.task.replace(scheduler.schedulePeriodicallyDirect(ibs, initialDelay, period, unit));
      }
  
      static final class IntervalBackpressureSubscription extends AtomicInteger
      implements Subscription, Runnable {
  
          private static final long serialVersionUID = -3871976901922172519L;
  
          final Subscriber<? super Long> downstream;
  
          final SequentialDisposable task;
  
          final AtomicLong requested;
  
          final AtomicLong available;
  
          long emitted;
  
          IntervalBackpressureSubscription(Subscriber<? super Long> downstream) {
              this.downstream = downstream;
              this.task = new SequentialDisposable();
              this.requested = new AtomicLong();
              this.available = new AtomicLong(-1L);
          }
  
          @Override
          public void request(long n) {
              if (SubscriptionHelper.validate(n)) {
                  BackpressureHelper.add(requested, n);
                  drain();
              }
          }
  
          @Override
          public void cancel() {
              task.dispose();
          }
  
          @Override
          public void run() {
              available.getAndIncrement();
              drain();
          }
  
          void drain() {
              if (getAndIncrement() == 0) {
                  int missed = 1;
                  SequentialDisposable t = task;
                  AtomicLong v = available;
                  long produced = emitted;
                  Subscriber<? super Long> a = downstream;
  
                  for (;;) {
                      long r = requested.get();
  
                      while (produced != r) {
                          if (t.isDisposed()) {
                              return;
                          }
                          if (v.get() >= produced) {
                              a.onNext(produced);
                              produced++;
                          } else {
                              break;
                          }
                      }
  
                      if (t.isDisposed()) {
                          return;
                      }
  
                      emitted = produced;
                      missed = addAndGet(-missed);
                      if (missed == 0) {
                          break;
                      }
                  }
              }
          }
      }
  }
  